This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cooperative Huntington's Disease Observational Research Trail (COHORT) is a study of patients and families with Huntington's Disease (HD). It is designed to learn more about when symptoms of HD develop and how fast the symptoms progress. It will do this by looking at the blood samples from different members of the same family with Huntington's Disease and comparing the results of genetic studies with their clinical findings and how they evolve over time. This study will include any individual with HD, or siblings, parents, or children of a person with HD. In addition, all the grandparents, grandchildren, or spouse of a person with HD, if this person is participating in the study, are eligible to participate. The study will involve a physical and neurological examination, measurement of vital signs, tests of thinking, coordination, movement, function, and a blood test. Additional components of the study are optional, and include additional blood or urine samples, filling out a questionnaire about other family members with HD. Participants will be seen once a year, and on follow-up visits will be asked to update the family history (if provided initially) and provide additional information on their general health. Subjects may ask to be informed about additional studies in HD or to receive informational updates between visits. It is envisioned that over time, this study will help understand the cause of HD, help develop treatment for it, and improve the ability of researchers to test new treatments quickly and accurately.